解析

①使用二分查詢
②使用hash

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<unordered_set>
using namespace std;
bool func(const vector<int>& data,int M) {
	for (int i = 0; i <data.size()-1; i++) {
		if (data[i] + data[data.
 
size()- 1] < M)
			continue;
		if (binary_search(data.begin() + i + 1, data.end(), M-data[i])) {
			printf("%d %d", data[i],M-data[i]);
			return true;
		}
	}
	return false;
}
int main()
{
	int N, M;

	scanf("%d %d", &N, &M);
	vector<int> data(N);
	for (int i = 0; i < N; i++)
		scanf
 
("%d", &data[i]);
	sort(data.begin(), data.end());
	if (func(data,M)== false)
		printf("No Solution");
}
/*
8 15
1 2 8 7 2 4 11 15
*/

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<unordered_map>
#include<unordered_set>
using
 
 namespace std;
int main()
{
	int N,M;
	scanf("%d %d", &N, &M);
	vector<int> data(N);
	for (int i = 0; i < N; i++)
		scanf("%d", &data[i]);
	unordered_map<int, int>  Map;
	for (auto x : data)
		Map[x]++;
	unordered_set<int> Set(data.cbegin(), data.cend());
	sort(data.begin(), data.end());
	bool flag = false;
	for (auto x : data) {
		if (Set.find(M-x) !=Set.end()) { //OK
			if (2*x==M && Map[x]<=1) 
				continue;
			flag = true;
			printf("%d %d", x, M - x);
			break;
		}
	}
	if (flag == false)
		printf("No Solution");
}